You don't have to give people things just because they are persistent, either. I think it's OK to be rude to creeps, but I don't like the notion that someone will think that their scheme is working.

But I also think that a lot of people who think someone is irritating gets convinced of their own bullshit and sees them as a threat unless people make it crystal clear what the difference is between a normal person who is unattractive, an obsessive, and a person who's either ten seconds away from abusing or raping someone.